/*
 * Copyright (C) 2006 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.io;

import java.io.Closeable;
import java.io.Flushable;
import java.io.IOException;
import java.io.Writer;

/**
 * Writer that places all output on an {@link Appendable} target. If the target
 * is {@link Flushable} or {@link Closeable}, flush()es and close()s will also
 * be delegated to the target.
 * 
 * @author Alan Green
 * @author Sebastian Kanthak
 * @since 2009.09.15 <b>tentative</b>
 */
class AppendableWriter extends Writer {
    private final Appendable target;
    private boolean closed;

    /**
     * Creates a new writer that appends everything it writes to {@code target}.
     * 
     * @param target
     *            target to which to append output
     */
    AppendableWriter(Appendable target) {
        this.target = target;
    }

    /*
     * Abstract methods from Writer
     */

    @Override
    public void write(char cbuf[], int off, int len) throws IOException {
        checkNotClosed();
        // It turns out that creating a new String is usually as fast, or faster
        // than wrapping cbuf in a light-weight CharSequence.
        target.append(new String(cbuf, off, len));
    }

    @Override
    public void flush() throws IOException {
        checkNotClosed();
        if (target instanceof Flushable) {
            ((Flushable) target).flush();
        }
    }

    @Override
    public void close() throws IOException {
        this.closed = true;
        if (target instanceof Closeable) {
            ((Closeable) target).close();
        }
    }

    /*
     * Override a few functions for performance reasons to avoid creating
     * unnecessary strings.
     */

    @Override
    public void write(int c) throws IOException {
        checkNotClosed();
        target.append((char) c);
    }

    @Override
    public void write(String str) throws IOException {
        checkNotClosed();
        target.append(str);
    }

    @Override
    public void write(String str, int off, int len) throws IOException {
        checkNotClosed();
        // tricky: append takes start, end pair...
        target.append(str, off, off + len);
    }

    @Override
    public Writer append(char c) throws IOException {
        checkNotClosed();
        target.append(c);
        return this;
    }

    @Override
    public Writer append(CharSequence charSeq) throws IOException {
        checkNotClosed();
        target.append(charSeq);
        return this;
    }

    @Override
    public Writer append(CharSequence charSeq, int start, int end)
            throws IOException {
        checkNotClosed();
        target.append(charSeq, start, end);
        return this;
    }

    private void checkNotClosed() throws IOException {
        if (closed) {
            throw new IOException("Cannot write to a closed writer.");
        }
    }
}
